Thoracic Vertebrae
The bodies of the thoracic vertebrae are relatively short but increase in length from the tenth caudally (see Fig. 12.4). The long spinous processes of the first half of the thoracic region are of about equal length.
Those of the second half gradually decrease in height; their caudal inclination changes at the eleventh thoracic, the anticlinal vertebra. A more noteworthy change occurs in the orientation of the articular surfaces. On the first 10 (or so) thoracic vertebrae these surfaces lie roughly in a dorsal plane (like those of the cervical vertebrae); caudal to this they are nearly sagittal, and the cranial articular processes enclose the caudal ones (see Fig. 2.10). The articular spaces of the former joints are best depicted in lateral radiographs (Fig. 12.5), and those of the latter, in ventrodorsal radiographs. The more cranial thoracic vertebrae favor lateral movement of the column, whereas the more caudal bones favor sagittal flexion and extension. Other features of the canine and feline vertebrae are the presence of the mammillary and accessory processes. The mammillary processes are short dorsal projections of the transverse processes that first appear at the third thoracic vertebra and, from the eleventh, migrate dorsally to surmount the cranial articular processes. The accessory processes arise from the caudal border of the pedicle and are present from the midthoracic to the midlumbar region; they are confined to the last three thoracic vertebrae in cats (see Fig. 2.11/1 and 2).
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